Advanced endovascular graft

ABSTRACT

This invention is a system for the treatment of body passageways; in particular, vessels with vascular disease. The system includes an endovascular graft with a low-profile delivery configuration and a deployed configuration in which it conforms to the morphology of the vessel or body passageway to be treated as well as various connector members and stents. The graft is made from an inflatable graft body section and may be bifurcated. One or more inflatable cuffs may be disposed at either end of the graft body section. At least one inflatable channel is disposed between and in fluid communication with the inflatable cuffs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation U.S. patent application Ser. No.10/091,641, filed Mar. 5, 2002, now abandoned, which is a continuationof U.S. patent application Ser. No. 10/029,559, filed Dec. 20, 2001, nowU.S. Pat. No. 7,147,661, the contents of which are incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to a system for the treatment of disordersof the vasculature. More specifically, the invention relates to a systemfor the treatment of disease or injury that potentially compromises theintegrity of a flow conduit in the body. For example, an embodiment ofthe invention is useful in treating indications in the digestive andreproductive systems as well as indications in the cardiovascularsystem, including thoracic and abdominal aortic aneurysms, arterialdissections (such as those caused by traumatic injury), etc. Suchcardiovascular indications often require intervention due to theseverity of the sequelae, which frequently is death. In addition, thisapplication is related to U.S. patent application Ser. No. 10/029,570,filed Dec. 20, 2001, entitled “Method and Apparatus for Shape FormingEndovascular Graft Material” by Chobotov et al., U.S. patent applicationSer. No. 10/029,584, filed Dec. 20, 2001, entitled “Endovascular GraftJoint and Method for Manufacture” by Chobotov et al., U.S. patentapplication Ser. No. 10/029,557, filed Dec. 20, 2001, entitled “Methodand Apparatus for Manufacturing an Endovascular Graft Section”, byChobotov et al. All of the above applications are commonly owned. All ofthe above applications are hereby incorporated herein by reference, eachin its entirety.

BACKGROUND

For indications such as abdominal aortic aneurysms, traditional opensurgery is still the conventional and most widely-utilized treatmentwhen the aneurysm's size has grown to the point that the risk ofaneurysm rupture outweighs the drawbacks of surgery. Surgical repairinvolves replacement of the section of the vessel where the aneurysm hasformed with a graft. An example of a surgical procedure is described byCooley in Surgical Treatment of Aortic Aneurysms, 1986 (W.B. SaundersCompany).

Despite its advantages, however, open surgery is fraught with highmorbidity and mortality rates, primarily because of the invasive andcomplex nature of the procedure. Complications associated with surgeryinclude, for example, the possibility of aneurysm rupture, loss offunction related to extended periods of restricted blood flow to theextremities, blood loss, myocardial infarction, congestive heartfailure, arrhythmia, and complications associated with the use ofgeneral anesthesia and mechanical ventilation systems. In addition, thetypical patient in need of aneurysm repair is older and in poor health,facts that significantly increase the likelihood of complications.

Due to the risks and complexities of surgical intervention, variousattempts have been made to develop alternative methods for treating suchdisorders. One such method that has enjoyed some degree of success isthe catheter-based delivery of a bifurcated stent-graft via the femoralarteries to exclude the aneurysm from within the aorta.

Endovascular repair of aortic aneurysms represents a promising andattractive alternative to conventional surgical repair techniques. Therisk of medical complications is significantly reduced due to theless-invasive nature of the procedure. Recovery times are significantlyreduced as well, which concomitantly diminishes the length and expenseof hospital stays. For example, open surgery requires an average six-dayhospital stay and one or more days in the intensive care unit. Incontrast, endovascular repair typically requires a two-to-three dayhospital stay. Once out of the hospital, patients benefiting fromendovascular repair may fully recover in two weeks while surgicalpatients require six to eight weeks.

Despite these and other significant advantages, however,endovascular-based systems have a number of shortcomings. Presentbifurcated stent-grafts require relatively large delivery catheters,often up to 24 French and greater in diameter. These catheters also tendto have a high bending stiffness. Such limitations result in the needfor a surgical cut-down to deliver the stent-graft and make deliverythrough the often narrow and irregular arteries of diseased vesselsdifficult and risky. Because of this, endovascular treatment of aorticaneurysmal disease is not available to many patients who could otherwisebenefit from it. For instance, women statistically tend to have smallervessels and therefore some are excluded from many current endovasculartherapies simply due to this reason. There is therefore a need for anendovascular stent-graft capable of being delivered via a smaller andmore flexible delivery catheter. Even greater advantages may be realizedif such an endovascular stent-graft is capable of being deliveredpercutaneously.

Further, an endovascular stent-graft must withstand tremendous pulsatileforces over a substantial period of time while remaining both seated andsealed within the vessel. In order to achieve these objectives, thedevice, which may comprise component parts and/or materials, must remainintact. The device must resist axial migration from the site ofdeployment while being subjected to significant pulsatile forces, and itshould have sufficient radial compliance to conform to the vesselanatomy within which it is deployed so as to prevent blood leakagebetween the device and the vessel wall at both its proximal, orcephalic, end as well as at its distal, or caudal end or ends (where thenet force may be retrograde). Such a device should conform to themorphology of the treated vessel, without kinking or twisting, over thelife of the patient.

SUMMARY

The present invention generally is directed to a system for theendovascular treatment of body passageways that includes a medicaldevice implantable within a body lumen such as a blood vessel. Someembodiments of this invention include an endovascular graft for treatingvascular disease.

One embodiment includes a graft with a graft body section having aproximal end and a distal end, and, disposed or affixed on at least oneend, a connector member having one or more connector member connectorelements. The connector member may be embedded within multiple layers ofthe graft body section. A stent may be coupled or affixed to the one ormore connector member connector elements via one or more stent connectorelements. The graft may include a proximal stent and connector memberonly, a distal stent and connector member only, or both proximal anddistal stents and their respective connector members.

Both the connector member connector elements and the stent connectorelements may have a proximal end and a distal end that comprise opposingshoulder portions. The graft may further have one or more couplingmembers, such as a wire coil, configured to couple or connect the one ormore connector member connector elements to the one or more stentconnector elements.

Both the connector members and the stents may be formed of a serpentinering having one or more apices. One embodiment includes a graft havingsingle stage distal and/or proximal stents in which the associatedconnector member may have twice as many apices as the stent. In anotherembodiment, the graft has two-stage distal and/or proximal stents withtwice as many apices in a first region as in a second region while theassociated connector member has the twice the number of apices as in thefirst region of the stent. For example, a useful embodiment is one inwhich a twelve-apex connector member is connected to a first six-apex orsix-crown region of a proximal or distal stent and that stent has asecond three-apex or three-crown region integral with or joined to thesix-crown region.

In alternative embodiments, grafts that include various combinations ofsingle and multiple-stage proximal and distal stents with theirassociated connector members are possible.

The stents may also include one or more barbs. Typically, the barbs on aproximal stent are oriented distally to engage the stent into the tissuewall in the proximal-to-distal flow field in which the graft istypically disposed. Likewise, in applications in which the graft isdeployed to treat an abdominal or thoracic aortic aneurysm, the barbs onone or more distal stents are typically oriented proximally to engagethe stent into the tissue wall to oppose the typically retrogrademigration forces. The barbs may range in length from about 1 to about 5mm. They will typically project radially outward from a longitudinalaxis of their respective stent and form a barb radial angle from about10 to about 45 degrees with respect to the graft proximal neck portioninlet axis when the stent is deployed in vivo. The barbs may also belaterally biased in a plane that is orthogonal to a plane in which thebarb radial angle is formed to form a barb kick angle.

The stent or stents (proximal and/or distal) comprise struts having oneor more optional barb tuck pads integral to the struts such that whenthe proximal stent is in a reduced profile delivery configuration, eachbarb is retained by the stent strut. When the endovascular graft is in adeployed configuration, the one or more barbs are released.

The stent or stents may also comprise optional barb tuck slotsconfigured to receive the barbs such that each barb is retained by aslot when the stent is in a delivery configuration. In a deployedconfiguration, the barbs are released from their corresponding barb tuckslots.

In addition, the stent may comprise grooves. In a typical deliverysystem, some type of belts or sutures may be used to help retain theendovascular graft in its compressed delivery configuration. The groovesmay accommodate these belts or sutures without increasing the smalldiameter delivery of the device.

The graft body section may also have one or more inflatable cuffsdisposed on or near the graft body section proximal end, distal end, orboth. The inflatable cuffs provide a sufficiently stiff structure wheninflated which help to support the graft body section and provide aconformable surface to seal the graft against the interior surface ofthe vessel in which it is deployed.

The graft body section may also include one or more inflatable channels.The channel or channels typically may be disposed between and in fluidcommunication with either or both proximal and distal inflatable cuffs.The channel or channels enhance the graft body section stiffness upontheir inflation, help to prevent kinking of the graft body section, andmay also facilitate deployment of the graft within a patient's bodypassageway. The inflatable channel or channels can be in a longitudinaland/or linear configuration with respect to the graft body section, butalternatively may take on a helical or circumferential configuration.Other orientations such as interconnecting grids or rings may also besuitable alone or in combination with any of the other configurations.

During deployment of the graft, the inflatable cuff or cuffs and channelor channels may be inflated or injected with a material that maycomprise one or more of a solid, fluid (gas and/or liquid), gel or othermedium. According to the invention, a useful inflation medium includesthe combination polyethylene glycol diacrylate, pentaerthyritol tetra3(mercaptopropionate) and a buffer such as glycylglycine ortriethanolamine in phosphate-buffered saline. Saline or another inertbiocompatible liquid may be added to this three-component inflationmedium in amounts up to about sixty percent of the total inflationmedium volume. Radiopaque materials such as tantalum, iodinated contrastagents, barium sulfate, etc. may be added to this three-componentmedium, typically in the buffer, so to render the inflation mediumvisible under fluoroscopy.

In another embodiment of the invention, the graft may comprise a mainbody portion and a first bifurcated portion forming a continuous lumenthat is configured to confine a flow of fluid therethrough. The graftmay also include a second bifurcated portion in fluid communication withthe main body portion. At least one inflatable cuff may be disposed ateither or both a proximal end of the main body portion and a distal endof the first bifurcated portion. One or more inflatable channels may bedisposed between the inflatable cuffs as previously described, and mayextend over some or all of the main body portion. The cuffs and channelsmay be filled with an inflation medium, optionally diluted with an inertbiocompatible material such as saline or other liquid, as describedabove.

In yet another embodiment of the invention, the graft may comprise amain body portion in fluid communication with a first and a secondbifurcated portion forming a continuous bifurcated lumen, said lumenconfigured to confine a flow of fluid therethrough. At least oneinflatable cuff may be disposed at or near either or both a proximal endof the main body portion and a distal end of the first and secondbifurcated portions. One or more inflatable channels may be disposedbetween the inflatable cuffs as previously described, and may extendover some or all of the main body portion.

The proximal ends of the graft main body portion may have connectormembers comprising one or more connector elements, and a proximal stentcoupled to the one or more connector elements. One or both of the firstand/or second bifurcated portions may likewise have first and/or seconddistal connector members comprising one or more connector elementsdisposed on their respective distal ends, and a distal stent coupled tothe first and/or second distal connector members.

The present invention is also a system for implanting a tubular medicaldevice within a body lumen having a wall, including a stent for affixingthe medical device to the body lumen wall and a connector member forcoupling the stent to the medical device, wherein the stent and theconnector member are coupled to one another by at least one set ofconnector elements.

One or more barbs may also be included in this system. In addition, oneor more barb tuck pads may be included in which the one or more barbsare configured to be retained by the one or more barb tuck pads when thesystem is in a delivery configuration and released by the one or morebarb tuck pads when the system moves to a deployed configuration. Thestent may further include optional slots configured to receive the barbswhen the system is in a delivery configuration and wherein the barbs areconfigured to be released from the slots when the system is in adeployed configuration.

The invention also includes an endovascular graft comprising a graftbody section with a proximal end and a distal end and a proximalconnector member affixed to the proximal end of the graft body section.The proximal connector member may have one or more connector elements.

The graft may also have a proximal stent comprising one or more distallyoriented barbs and one or more proximal stent connector elements coupledto the one or more proximal connector member connector elements and adistal connector member affixed to the distal end of the graft bodysection. The distal connector member may include one or more connectorelements.

The graft of this embodiment further includes a distal stent comprisingone or more proximally oriented barbs and comprising one or more distalstent connector elements coupled to the one or more distal connectormember connector elements, one or more inflatable cuffs disposed at ornear each of the proximal and distal ends of the graft body section, andwherein the graft body section comprises an inflatable channel in fluidcommunication with the proximal and distal cuffs.

In addition, the proximal and distal connector member connector elementsmay each have opposing shoulder portions on their proximal and distalends, as may the proximal and distal stent connector elements. One ormore coupling members may couple the proximal connector member connectorelements to the proximal stent connector elements and likewise couplethe one or more distal connector member connector elements to the one ormore distal stent connector elements.

At least one of the inflatable channel, the distal inflatable cuff, andthe proximal inflatable cuff may contain an inflation medium comprisingthe combination polyethylene glycol diacrylate, pentaerthyritol tetra3(mercaptopropionate), and a buffer.

The proximal stent barbs or distal stent barbs of this embodiment mayhave a length from about 1 to about 5 mm, and the graft body section maycomprise ePTFE.

In yet still a further bifurcated embodiment of the present invention,the device includes a main body portion with a distal end and a proximalend with a connector member disposed on the proximal end. The connectormember may include one or more connector elements.

The proximal stent of this embodiment may comprise one or more distallyoriented barbs and one or more proximal stent connector elements thatare coupled to the connector member connector elements.

This embodiment further includes a first bifurcated portion and a secondbifurcated portion forming a continuous lumen with the main bodyportion. This lumen is configured to confine a flow of fluidtherethrough.

A distal connector member may be disposed on distal ends of each of thefirst and second bifurcated portions. Each of these distal connectormembers includes one or more connector elements. In addition, thisembodiment has one or more distal stents with at least one proximallyoriented barb and comprising one or more distal stent connectorelements. The distal stent connector elements are coupled to the distalconnector member connector elements on one or both of the first andsecond bifurcated portions.

This embodiment also includes at least one inflatable channel extendingfrom one or both of the first and second bifurcated portions to the mainbody portion, at least one inflatable cuff disposed at or near aproximal end of the main body portion in fluid communication with the atleast one channel, and an inflatable cuff disposed at or near a distalend of each of the first and second bifurcated portions.

The proximal and distal connector member connector elements may eachhave opposing shoulder portions on their proximal and distal ends, asmay the proximal and distal stent connector elements. One or morecoupling members may couple the proximal connector member connectorelements to the proximal stent connector elements and likewise couplethe one or more distal connector member connector elements to the one ormore distal stent connector elements.

At least one of the inflatable channel, the first bifurcated portiondistal inflatable cuff, the second bifurcated portion distal inflatablecuff, and the proximal inflatable cuff may contain an inflation mediumcomprising the combination polyethylene glycol diacrylate,pentaerthyritol tetra 3 (mercaptopropionate), and a buffer.

The proximal and/or distal stent barbs may have a length from about 1 toabout 5 mm. The graft main body portion as well as the first and secondbifurcated portions may comprise ePTFE.

These and other advantages of the invention will become more apparentfrom the following detailed description of the invention when taken inconjunction with the accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an endovascular graft according to an embodiment of thepresent invention.

FIGS. 1A-1B detail two angles at which a stent barb may be oriented onthe graft of an embodiment of the present invention.

FIG. 2 shows a second endovascular graft according to an embodiment ofthe present invention.

FIG. 3 shows a flat pattern of a component of the endovascular graft ofFIG. 2.

FIG. 4 shows a flat pattern of another component of the endovasculargraft of FIG. 2.

FIG. 5 shows a flat pattern of a portion of the endovascular graft ofFIG. 2.

FIG. 5A is an enlarged side view of a portion of the endovascular graftof FIG. 5.

FIG. 6 is an enlarged view of a portion of an endovascular graft havingfeatures of an embodiment of the present invention.

FIG. 7 shows a bifurcated endovascular graft according to embodiments ofthe present invention.

FIG. 8 shows a flat pattern of yet another component of the endovasculargraft of FIG. 2.

FIG. 9 shows a flat pattern of another component of the endovasculargraft of FIG. 2.

FIG. 10 shows detail of a stent apex detail that comprises offsetcircular and elliptical radii.

FIG. 11 shows detail of a stent apex detail that comprises offsetcircular radii.

FIG. 12 shows detail of a stent section comprising a tapered strutsection.

FIG. 13 shows detail of a stent section comprising another configurationfor a tapered strut section.

DETAILED DESCRIPTION

FIG. 1 shows an endovascular graft 10 in its deployed configuration.Unless otherwise stated, the term “graft” or “endovascular graft” isused herein to refer to a prosthesis capable of repairing and/orreplacing diseased vessels or portions thereof, including generallytubular and bifurcated devices and any components attached or integralthereto. For purposes of illustration, the graft embodiments describedbelow are assumed to be most useful in the endovascular treatment ofabdominal aortic aneurysms (AAA). For the purposes of this application,with reference to endovascular graft devices, the term “proximal”describes the end of the graft that will be oriented towards theoncoming flow of bodily fluid, typically shows a flat pattern blood,when the device is deployed within a body passageway. The term “distal”therefore describes the graft end opposite the proximal end. Finally,while the drawings in the various figures are accurate representationsof the various embodiments of the present invention, the proportions ofthe various components thereof are not necessarily shown to exact scalewithin and among or between any given figure(s).

Graft 10 has a proximal end 11 and a distal end 12 and includes agenerally tubular structure or graft body section 13 comprised of one ormore layers of fusible material, such as expandedpolytetrafluoroethylene (ePTFE). A proximal inflatable cuff 16 isdisposed at or near a proximal end 14 of graft body section 13 and anoptional distal inflatable cuff 17 is disposed at or near a graft bodysection distal end 15. Graft body section 13 forms a longitudinal lumen22 configured to confine a flow of fluid therethrough and may range inlength from about 5 to about 30 cm; specifically from about 10 to about20 cm.

As will be described in greater detail below, inflation of cuffs 16 and17 will cause them to assume a generally annular shape (especially whengraft body section 13 is in an unconstrained state). Inflatable cuffs 16and 17 will generally, however, conform to the shape of the vesselwithin which it is deployed. When fully inflated, cuffs 16 and 17 mayhave an outside diameter ranging from about 10 to about 45 mm;specifically from about 16 to about 32 mm.

At least one inflatable channel 18 may be disposed between and in fluidcommunication with proximal inflatable cuff 16 and distal inflatablecuff 17. Inflatable channel 18 provides structural support to graft bodysection 13 when inflated to contain an inflation medium. Inflatablechannel 18 further prevents kinking and twisting of the tubularstructure or graft body section when it is deployed within angled ortortuous anatomies as well as during remodeling of body passageways(such as the aorta and iliac arteries) within which graft 10 isdeployed. Together with proximal and distal cuffs 16 and 17, inflatablechannel 18 forms a network of inflatable cuffs and channels in fluidcommunication with one other.

We have found the helical configuration of channel 18 in the FIG. 1embodiment to be particularly effective in providing the needed kinkresistance for effectively treating diseased body passageways such asAAAs, in which highly angled and tortuous anatomies are frequentlyfound. In alternative embodiments, however, other cuff and channelconfigurations are possible. Inflatable channel 18 may be disposedhelically as shown in FIG. 1, it may take on a more circumferential orannular rib and spine configuration as shown in the FIG. 2 embodiment,or otherwise. Similarly, the longitudinal and radial dimensions ofinflatable channel 18 may vary as necessary both between different graftbody sections and even within a single graft body section, depending onthe indication for which graft 10 is intended to treat. Further,inflatable channel 18 may be oriented at various angles with respect tothe longitudinal axis 25 of graft body section 13, and the pitch (thedistance between helical or parallel windings of channel 18) may vary asnecessary.

In the embodiment of FIG. 1, the channel pitch, or distance between eachhelical inflatable channel 18 winding, may range from about 2 to about20 mm, depending on the overall size of graft body section 13 and thedesired degree of kink resistance. We have found that a pitch of betweenabout 4 and about 10 mm is effective for tubular embodiments of thepresent invention and a pitch of between about 3 and about 10 mm to beuseful in bifurcated graft embodiments. The helix angle of each channelwinding (measured with respect to a plane perpendicular to the graftbody section longitudinal axis 25) may range from about 10 to about 45degrees; more specifically, from about 20 to about 35 degrees in tubularand bifurcated graft embodiments. Finally, the width of inflatablechannel 18 typically ranges from about 1 to about 8 mm; morespecifically, from about 2 to about 4 mm.

Graft body section or tubular structure 13 and its associated componentsmay be made from a variety of suitable materials, including ultra highmolecular weight polyethylene, polyesters, and the like. As previouslydiscussed, we have found constructing graft body section 13 primarilyfrom one or more layers of ePTFE to be particularly useful. Details ofhow graft 10 may be fabricated (as well as all of the other graftsdiscussed herein) are more fully described in parent U.S. patentapplication Ser. No. 10/029,559 and in U.S. patent application Ser. Nos.10/029,570, 10/029,584, and 10/029,557, each to Chobotov et al. and, inaddition, U.S. patent application Ser. No. 09/133,978 to Chobotov, filedFeb. 9, 1998 and entitled “Endovascular Graft”, now U.S. Pat. No.6,395,019 and U.S. patent application Ser. No. 09/917,371 to Chobotov etal., filed Jul. 27, 2001 and entitled “Bifurcated Stent-Graft DeliverySystem and Method”, now U.S. Pat. No. 6,761,733, the entirety of each ofwhich is hereby incorporated herein by reference, teach a usefulendovascular stent-graft and delivery system, respectively.

A proximal neck portion 23 is disposed in the vicinity of graft bodysection proximal end 14 and serves as an additional means to help sealthe deployed graft against the inside of a body passageway. Proximalneck portion 23 has an inlet axis 27 that forms an inlet axis angle α inrelation to graft body section longitudinal axis 25. This angled inletaxis 27 allows the graft to better conform to the morphology of apatient's vasculature in patients who have an angled vessel morphology,such as is often the case in the neck region of abdominal aorticaneurysms. The inlet axis angle α may range in any direction withrespect to longitudinal axis 25 from about zero to about 90 degrees,preferably from about 20 to about 30 degrees. Proximal neck portion 23may be tapered or flared to a larger diameter in the proximal directionto facilitate this sealing function. Proximal neck portion 23 alsoserves as a means of providing a smooth fluid flow transition into graftlumen 22.

The network of inflatable cuffs 16, 17 and channel 18 may be inflated,most usefully in vivo, by introduction or injection of a material ormedium through an injection port 33 that is in fluid communication withcuff 17 and the associated cuff/channel network. The material maycomprise one or more of a solid, fluid (gas and/or liquid), gel or othermedium. The material may contain a contrast medium that facilitatesimaging the device while it is being deployed within a patient's body.For example, radiopaque materials containing elements such as bismuth,barium, gold, iodine, platinum, tantalum or the like may be used inparticulate, liquid, powder or other suitable form as part of theinflation medium. Liquid iodinated contrast agents are a particularlysuitable material to facilitate such imaging. Radiopaque markers mayalso be disposed on or integrally formed into or on any portion of graft10 for the same purpose, and may be made from any combination ofbiocompatible radiopaque materials.

A connector member 24 is affixed to or integrally formed in graft bodysection 13, or as shown in FIG. 1, at or near graft body sectionproximal end 14 and proximal neck portion 23. Connector member 24 is aserpentine ring structure comprising apices 28. Connector member 24 maybe made from any suitable material that permits expansion from aconstrained state, most usefully a shape memory alloy havingsuperelastic properties such as nickel titanium (NiTi). Other suitableconnector member 24 materials include stainless steel, nickel-cobaltalloys such as MP35N, tantalum and its alloys, polymeric materials,composites, and the like. Connector member 24 (as well as all stents andconnector members described herein) may be configured to self-expandfrom a radially constrained state or be configured to expand as a resultof an applied force (such as from an inflated balloon), or, in the caseof some shape memory materials, a temperature change.

The configuration of connector member 24 shown in FIG. 1 comprises eightapices 28 (put more precisely, the FIG. 1 connector member 24 compriseseight proximal apices and eight distal apices; however, unless otherwisementioned, the term “apices” refers in this context to either theproximal or distal set of apices in a single connector member, stent, orstent portion). Another particularly useful configuration is one shownin FIGS. 2-7 in which the connector member comprises twelve apices. Anynumber of apices up to twenty-four or more may be used in connectormember 24. In general terms, as the number of apices 28 on connectormember 24 increase, connector member 24 will exhibit a greaterconformability to the vessel wall when it is expanded from a radiallyconstrained state.

No matter the number of apices present, one function of connector member24 is to work in conjunction with proximal neck 23 in which it istypically embedded to help seal the deployed graft against the inside ofa body passageway as previously described. It can also play a role inhelping to keep graft 10 in place within the vessel wall and may alsofacilitate the opening of graft body section proximal end 14 duringdeployment.

Some apices 28 may also comprise a connector member connector element30, described more fully below with respect to the embodiment of FIG. 2.In the FIG. 1 embodiment, in which connector member 24 comprises eight(proximal) apices 28, a connector element 30 is distributed on everyother apex 28. We have found this configuration to be suitable formeeting the various performance requirements of the present invention.Other configurations are possible, including the twelve-apex connectormember 24 shown in FIGS. 2-7 comprising six connector elements 30distributed on every other apex 28. Other configurations in which, forexample, connector elements are distributed on every apex, every thirdor fourth apex, or any other pattern are within the scope of the presentinvention.

Graft 10 further comprises a proximal stent 40 having a proximal end 42and a distal end 44. Although other configurations are possible,proximal stent 40 in the FIG. 1 embodiment comprises a serpentine ringhaving four apices 46, or half the number of apices 28 of connectormember 24. Note that proximal stent 40 in FIG. 1 takes on an optionaltulip-shaped tapered profile in which the stent's diameter varies alongits length. Such a profile serves to present sufficient radial forceupon radial expansion of stent 40 to reliably anchor graft 10 to thevessel or lumen wall within which it is deployed while, at its tapereddistal end near graft body section 13, refraining from interfering withthe sealing function performed by proximal cuff 16, proximal neckportion 23, and connector member 24. This profile also accommodates anytaper that may be present in the host vessel or lumen.

As shown in FIG. 1, proximal stent 40 is disposed generally proximal tograft body section 13 and connector member 24. Proximal stent istypically, though not necessarily, made a part of graft 10 by beingaffixed or connected to connector member 24 via connector elements asdescribed in detail below. Proximal stent 40 may also be affixed orembedded directly to or in proximal neck portion 23 and/or otherportions of graft body section 13. In addition, the present inventionincludes embodiments wherein the connector member and proximal stent arenot mechanically or otherwise fastened to one another but ratherunified, formed of a monolithic piece of material such as NiTi.

This configuration of proximal stent 40, connector member 24, proximalneck portion 23, and proximal cuff 16 helps to separate the sealingfunction of proximal cuff 16, which requires conformation and appositionto the vessel wall within which graft 10 is deployed without excessiveradial force, from the anchoring function of proximal stent 40(connector member 24 and proximal neck portion 23 play intermediateroles). This allows the sealing and anchoring functions each to beoptimized without compromising the other. In addition, in part becauseproximal stent 40, connector member 24, and inflatable cuff 16 arelongitudinally distributed along the graft body section longitudinalaxis 25, a smaller, more flexible delivery profile ranging from about 10to about 16 French is possible; preferably below 12 French.

Proximal stent 40 may be manufactured from any of the materials suitablefor connector member 24. When manufactured from a shape memory alloyhaving superelastic properties such as NiTi, proximal stent 40 may beconfigured to self-expand upon release from a constrained state.

Proximal stent 40 further comprises proximal stent connector elements 48that are affixed to connector member connector elements 30 via couplingmembers as described more fully below in relation to FIGS. 2-6. Notethat in the FIG. 1 embodiment, there is one proximal stent connectorelement 48 for every connector member connector element 30.

Proximal stent 40 also comprises struts 41 and may also comprise one ormore barbs 43. A barb can be any outwardly directed protuberance,typically terminating in a sharp point that is capable of at leastpartially penetrating a body passageway in which graft 10 is deployed(typically the intimal and medial layers of a blood vessel such as theabdominal aorta).

When proximal stent 40 is deployed in the abdominal aorta, for example,typically in a location proximal to the aneurysm and any diseasedtissue, barbs 43 are designed to work in conjunction with thedistally-oriented blood flow field in this location to penetrate tissueand prevent axial migration of graft 10. This is why barbs 43 in theFIG. 1 embodiment are oriented distally with respect to graft bodysection 13.

In alternative embodiments, depending upon the material used in themanufacture of proximal stent 40, the clinical demands and otherfactors, the degree to which barbs 43 help maintain the position ofgraft 10 within the vessel may vary. Consequently, the number,dimensions, configuration and orientation of barbs 43 may varysignificantly, yet be within the scope of the present invention.

The length of barbs 43 in any of the embodiments of the presentinvention may range from about 1 to about 5 mm; more particularly, fromabout 2 to about 4 mm.

As shown in their free expanded configuration in FIG. 1 and as shown ingreater detail in FIG. 1A, barbs 43 may be oriented in a distaldirection and form an elevation angle β ranging from about 10 to about45 degrees or higher with respect to a longitudinal axis 29 of strut 41,projecting generally radially outward from graft lumen 22 away fromproximal neck inlet axis 27. Disposing barbs at angle β provides thenecessary embedding force to anchor graft 10 into the vessel or lumen inwhich it is deployed. Although not shown in the figures, the barbelevation may also be described when the graft 10 is deployed in vivo ina body lumen or vessel by a second angle β′ measured relative toproximal neck inlet axis 27. This second barb elevation angle β′ willtypically range from about 5 to about 45 degrees. For both barbelevation angles β and β′, similar orientations may be found with barbsin other embodiments of the present invention.

It is generally desirable that barbs 43 be oriented in a positiongenerally parallel to the axis of the lumen in which they are deployedso that they are in a position to best resist the drag loads imposed bythe flow field in vivo in certain applications. To this end, we havefound it useful for one or more of barbs 43 to form an optional secondbarb azimuth or “kick” angle γ with respect to strut longitudinal axis29 as shown in FIG. 1B. In this view, barb 43 is laterally biased in aplane that is tangent to an outside surface 37 of strut 41 and generallyorthogonal to a plane in which angle γ is formed. The term “strutoutside surface 37” generally refers to that portion of the surface ofstrut 41 located opposite the proximal neck inlet axis 27, or thatportion of strut 41 that when deployed will be in direct contact withthe vessel or lumen wall. We have also found that providing lateral kickangle γ to barbs 43 contributes to greater barb stability when the barbis tucked behind an adjacent strut or tuck pad in a reduced diameterdelivery configuration. In proximal stent 40, γ may range from betweenabout 5 and about 70 degrees relative to strut axis 41. Similarorientations may be found with barbs in other embodiments of the presentinvention.

The number of barbs, the length of each barb, each of the barb anglesdescribed above, and the barb orientation may vary from barb to barbwithin a single stent or between multiple stents within a single graft.

Note that although the various barbs (and tuck pads 45 discussed below)discussed herein may be attached to or fixed on the stent struts 41, wehave found it useful that, as shown in the various figures, they beintegrally formed as part of the stent struts. In other words, they canbe mere extensions of the struts in which no joint or other connectionexists. Because there is no joint, we have found the strength of thebarb/strut interface to be very high, as is the fatigue resistance ofthe barbs. With no mechanical connection to join the barbs to thestruts, reliability of the barb/strut interface is higher. In addition,the lack of a heat-affected zone in which the mechanical properties of awelded or brazed joint may be deleteriously affected is anothersignificant advantage to having the barbs and tuck pads be integral tothe stent.

Struts 41 may also comprise optional integral tuck pads 45 disposedopposite each barb 43. As is the case with the barbs, the number,dimensions, configuration and orientation of barb tuck pads 45 may varysignificantly.

During preparation of graft 10 (and therefore proximal stent 40) intoits reduced diameter delivery configuration, each barb 43 is placedbehind a corresponding strut 41 (and optional tuck pad 45, if present)so to thereby prevent that barb from contacting the inside of a deliverysheath or catheter during delivery of the device and from undesiredcontact with the inside of a vessel wall. As described in U.S. patentapplication Ser. No. 09/917,371 to Chobotov et al., now U.S. Pat. No.6,761,733, a release belt disposed in one or more grooves 35 disposed onstruts 41 retain proximal stent 40 in this delivery configuration.

Upon deployment of graft 10, and more particularly, proximal stent 40,(typically accomplished in part by release of this and other belts), theradial expansion of stent 40 results in a displacement of struts 41 sothat the distance between them increases. Eventually this displacementbecomes large enough so to free the barbs from behind the adjacent strut(and optional tuck pad 45, if present) and engage the wall of the lumenbeing treated. During experiments in which stents of the presentinvention having barbs described herein are released from a constraineddelivery configuration to assume an expanded or deployed configuration,high speed video confirms that the barbs tend to release with a timeconstant that is generally an order of magnitude lower than the timeconstant associated with the radial expansion of the stent. In otherwords, during the stent deployment process, their barbs complete theirdeployment before the stent is fully expanded, so that the barbs mayengage the vessel or lumen wall with maximum effectiveness.

Alternatively, and especially in the case when a different material suchas stainless steel is used for proximal stent 40, an optional balloonmay be used to expand stent 40 to free barbs 43 from their tuck pads 45and to cause barbs 43 to engage tissue as desired. Even if asuperelastic self-expanding proximal stent 40 is used in graft 10, sucha balloon may be used to help further implant barbs 43 into theirdesired position to ensure proper placement of graft 10.

Turning now to FIG. 2, another endovascular graft having features of thepresent invention is illustrated. Graft 50 has a proximal end 51 and adistal end 52 and comprises a tubular structure or graft body section 53with a proximal end 54 and distal end 55. As with the FIG. 1 embodiment,graft body section 53 forms a longitudinal lumen 73 configured toconfine a flow of fluid therethrough and may range in length from about5 to about 30 cm; specifically from about 10 to about 20 cm. Proximalinflatable cuff 56 and optional distal inflatable cuff 57 form a sealwhen inflated to help prevent transmission of pressure (hemodynamicpressure when the fluid is blood) to the lumen or vessel walls in theregion between the proximal and distal cuffs. In addition, the cuffshelp to prevent flow of fluid such as blood around the outer surface ofgraft body section 53.

Inflatable channel 58 comprises an inflatable longitudinal channel orspine in fluid communication with a series of approximately parallelinflatable circumferential channels or ribs. We have found thisconfiguration to be particularly useful in providing effective kinkresistance while allowing for rapid and relatively easy inflation of thecuffs and channels when using more viscous inflation materials. Channel58 is in fluid communication with proximal and distal cuffs 56 and 57,forming a network of inflatable cuffs and channels in fluidcommunication with each other. Fill port 59 is in fluid communicationwith distal cuff 57, inflatable channel 58, and proximal cuff 56, addingto this network for the introduction of an inflation medium into graftbody section 53. Features of the FIG. 1 embodiment not discussed hereinmay be present in the FIG. 2 device.

Graft 50 of FIG. 2 also comprises a twelve-crown or twelve-apex proximalconnector member 60, a two-stage six- and three-crown proximal stent 70,distal neck portion 77, distal connector member 124, and distal stent128. Distal connector member 124 and distal stent 128 are analogous toconnector member 60 and proximal stent 70 except that the distal stentin the FIG. 2 embodiment is single-stage and its optional barbs face inthe opposite, or proximal direction relative to the barbs 74 of proximalstent 70. Distal connector member 124 is affixed or attached to distalstent 128, both of which are more fully described in relation to abifurcated version of the present invention shown in FIGS. 8 and 9,respectively. Distal connector member 124 and distal stent 128 may bemanufactured from materials and according to methods that are suitablefor connector member 60 and proximal stent 70. Further, distal connectormember 124 may be attached to, affixed to, formed integrally withtubular structure or graft body section 53, or more typically, distalneck portion 77. Distal connector member 124 further comprises fill portbridge 132.

FIG. 3 shows a detailed flat pattern view of the proximal connectormember 60 shown in FIG. 2. Proximal connector member 60 comprises adistal end 66 and a proximal end 64 having twelve crowns or apices 65.Alternate proximal apices 65 comprise proximal connector memberconnector elements 62. These connector elements 62 each in turncomprises a proximal end 61, a distal end 63, and optional ears 80disposed near distal end 63. Ears 80 provide for increased surface areaon connector elements 62 to aid in maximizing the strength of the bondbetween connector element and graft proximal neck portion and furthercomprises one or more optional apertures 82 to further enhance such abond as previously discussed. Opposing shoulder portions 84 may haverounded corners so to minimize their potential to snag, tear, orotherwise interfere with other components of the graft or the lumen inwhich it is deployed. Shoulder portions 84 also have one or moreoptional shoulder holes 85. These shoulder holes 85 are useful inhelping to stabilize the proximal stent 70 and proximal connector member60 device as they are coupled during assembly as discussed below inconjunction with FIG. 5A.

As illustrated in FIGS. 4-5 and 6-7, two-stage proximal stent 70 has aproximal end 76 and a distal end 77 with proximal stent connectorelements 72. Proximal stent connector elements 72 have opposing shoulderportions 78 that may mirror opposing shoulder portions 84 of distalstent connector elements 62.

Proximal stent 70 comprises struts 71, any one of which may furthercomprise one or more barbs 74. Optional barb tuck pads 86 near each barbserve to shield barbs 74 when graft 50 is in its reduced diameterdelivery configuration. Struts 71 or tuck pads 86 may also contain anoptional barb tuck slot 85 to help retain barbs 74 while graft 50 (andconsequently proximal stent 70) is in its delivery configuration. Upondeployment of graft 50 as previously described with respect to the FIG.1 embodiment, barbs 74 are released from barb tuck slots 85 and areplaced in their operational, or deployed configuration, as shown inFIGS. 2 and 6. When so deployed in a patient vessel, proximal stent 70is expanded, forcing barbs 74 at least partially into the vessel wall toemplace graft 50 therein and to resist fluid flow forces that mightotherwise dislodge graft 50.

Proximal stent 70 also may comprise one or more sets of optional grooves87 for housing device release bands as previously discussed.

Unlike proximal stent 40 of FIG. 1, however, proximal stent 70 is atwo-stage component having a first, or six-crown region 90 and a second,or three-crown region 92. The first, or six-crown region 90 comprises aserpentine ring having six apices 94 (i.e., six distal and six proximalapices). Likewise, the second, or three-crown region 92 comprises aserpentine ring having three apices 93, the distal apices of whichconnect to every other proximal apex 94 of six-crown region 90. Notethat proximal stent 70 is typically made from a single piece of materialsuch that there are no joints or connections between each stage (such asa mechanical connection or a weld, etc.). However, other configurationsin which two or more stages may be so joined or connected from separateparts or stents to form a single stent are possible; likewise,single-piece stents having more than two stages are also possible.

Proximal stent 70 may exhibit a greater outward radial force atthree-crown region 92 than in six-crown region 90. Such a design isparticularly useful in a clinical setting in which it is desired thatsuch outward radial force be applied within a healthier section ofvessel, more remote from the site of disease. Proximal stent 70 mayaccordingly perform the anchoring function within a portion of vesselthat can accommodate such radial force.

FIG. 5 is a flat pattern view of connector member 60 joined to proximalstent 70. For this embodiment, there is a relationship among the variousapices 65, 93 and 94 of the connector member 60 and the two stages ofproximal stent 70, respectively, in which there are twelve connectormember apices 65, six apices 94 in the proximal stent first or six-crownregion 90 and three apices 93 in the proximal stent second orthree-crown region 92.

While the actual number of apices may vary as previously discussed, thismore generally illustrates a useful convention for the present inventionin which the relationship among the various apices may be described: forinstance, if the number of connector member 60 apices 65 is denoted “n”,“n/2” then denotes the number of proximal stent 70 first or six-crownregion 90 apices 94 and “n/4” as the number of proximal stent 70 secondor three-crown region 92 apices 93. Other useful embodiments includethose in which there are “n” connector member apices, “n” proximal stentfirst region apices, and “n/2” proximal stent second region apices.These ratios may vary as appropriate; these particular sets of ratiosare merely illustrative.

Note also in FIG. 5 that connector member connector elements 62 arecoupled to proximal stent connector elements 72 via coupling members 54.

FIG. 5A is a side view of proximal stent connector element 72, connectormember connector element 62, and coupling member 54. Coupling member 54is a wire or similar element wrapped to form a coil around theoverlapping connector member connector element 62 and proximal stentconnector element 72 to mechanically join connector member 60 toproximal stent 70. Alternatively, any other suitable joining technique,such as welding, brazing, soldering, mechanical means, adhesive, etc.may be used to join these components of the graft 50. We have found,however, that mechanical means such as coupling member 54 is most usefulin that it avoids problems presented by techniques such as welding,etc., where possible heat-affected zones some distance from the jointmay deleteriously affect the microstructure of the stent/connectorelement material, especially when that material is nickel titanium, thushaving a negative impact on the joint strength, fatigue life, andultimately the integrity of graft 50.

Any suitable member may be used for coupling member 54 although we havefound a wire or wire-like member having a circular cross-sectional shapeto be useful (although any shape may be used). Optimally, the wirecoupling member 54 may be formed of a suitable metal such as nickel,stainless steel, nickel-titanium, etc. The wire may have a diameterranging from about 0.002 to about 0.006 inch; more specifically fromabout 0.003 to about 0.005 inch.

To secure the connector elements 62 and 72 to one another, couplingmember 54 may be wound around the matched connector elements one or moretimes. We have found that providing enough windings to present a singlelayer of wire in which the windings are immediately adjacent one anotherfrom shoulder 78, 84 to shoulder 78, 84 provides sufficient strength andstiffness to the joint thus created without detracting from the lowdelivery profile afforded by the novel design of graft 50. Thus thenumber of optimal windings from graft to graft will vary but typicallyranges from about 6 to about 18 windings in most applications. Withcoupling members 54 in place, connector member connector elements 62 andproximal stent connector elements 72 are securely coupled to oneanother. The features and advantages of coupling member 54 discussedherein may be utilized by any of the embodiments of the presentinvention herein discussed.

FIG. 6 is a perspective view of connector member 60 joined to proximalstent 70 in this way in their expanded, or deployed configuration. Graftbody section 53 and other graft components are removed for clarity ofillustration. Barbs 74 are shown in their deployed state, released fromoptional barb tuck pads 86.

FIG. 7 illustrates another embodiment of the invention in the form of abifurcated endovascular graft 100. A bifurcated device such asendovascular graft 100 may be utilized to repair a diseased lumen at ornear a bifurcation within the vessel, such as, for example, in the caseof an abdominal aortic aneurysm in which the aneurysm to be treated mayextend into the anatomical bifurcation or even into one or both of theiliac arteries distal to the bifurcation. In the following discussion,the various features of the graft embodiments previously discussed maybe used as necessary in the bifurcated graft 100 embodiment unlessspecifically mentioned otherwise.

Graft 100 comprises a first bifurcated portion 114, a second bifurcatedportion 115 and main body portion 116. The size and angular orientationof the bifurcated portions 114 and 115, respectively, may vary—evenbetween portion 114 and 115—to accommodate graft delivery systemrequirements and various clinical demands. For instance, each bifurcatedportion or leg is shown in FIG. 7 to have a different length, but thisis not necessary. First and second bifurcated portions 114 and 115 aregenerally configured to have an outer inflated diameter that iscompatible with the inner diameter of a patient's iliac arteries. Firstand second bifurcated portions 114 and 115 may also be formed in acurved shape to better accommodate curved and even tortuous anatomies insome applications.

Together, main body portion 116 and first and second bifurcated portions114, 115 form a continuous bifurcated lumen, similar to lumens 22 and73, which is configured to confine a flow of fluid therethrough. Andalthough not shown in FIG. 7, graft 100 does not have to have a secondbifurcated portion 115, in which case the bifurcated lumen is formedbetween main body portion 116 and first bifurcated portion 114.

First and second bifurcated portions 114 and 115 each comprises anetwork of inflatable cuffs and channels as discussed with respect tothe FIG. 2 embodiment, including inflatable channel 113. Channel 113comprises one or more optional inflatable longitudinal channels 110 influid communication with one or more approximately parallel inflatablecircumferential channels 144, all of which are in fluid communicationwith optional distal inflatable cuffs 117 and 119.

As with the embodiments previously discussed, the number of inflatablecircumferential channels 144 may vary with the specific configuration ofthe graft as adapted to a given indication. Generally, however, thenumber of inflatable circumferential channels 144 per bifurcated portionmay range from 1 to about 30, preferably about 10 to about 20.Similarly, the dimensions, spacing, angular orientation, etc. ofcircumferential inflatable channels 144 may vary as well.

For instance, the distance between and width of each circumferentialinflatable channel 144 may vary along the length of the graft or may beconstant. The pitch or inter-ring distance may range from about 2 toabout 20 mm; specifically, it may range from about 3 to about 10 mm.Circumferential inflatable channels 144 are each typically between about2 and about 4 mm wide, but may be from about 1 to about 8 mm wide. Eachlongitudinal channel 110 is typically from about 2 to about 4 mm wide,but may vary, together or independently, to be from about 1 to about 8mm wide.

In the embodiment of FIG. 7, channel 113 forms a continuous cuff andchannel network extending from first bifurcated portion 114 to main bodyportion 116 to second bifurcated portion 115. Accordingly, inflatablechannel 113 fluidly connects into a network with proximal inflatablecuff 111, secondary proximal cuff 112, circumferential inflatablechannels 144, optional distal inflatable cuff 117 and optional distalinflatable cuff 119. Note that longitudinal channels 110 extendproximally along main body portion 116 to be in fluid communication withcuffs 111 and 112.

In alternative embodiments of the graft of FIG. 7 as well as that ofFIGS. 1 and 2, numerous other inflatable channel and cuff configurationsare possible. The inflatable channel for instance may be disposedlongitudinally, horizontally, in a helical fashion, or otherwise. One ormore additional cuffs may be disposed on either or both bifurcatedportions 114 and 115 as well as main body portion 116. In otherembodiments, graft 100 may have compartmentalized channels and cuffsrequiring multiple sites from which they are inflated and may usemultiple inflation materials to optimize properties in each region.

Second bifurcated portion 115 may be of a similar construction to firstbifurcated portion 114. In the FIG. 7 embodiment of graft 100, secondbifurcated portion 115 is of a unitary, continuous construction withfirst bifurcated portion 114 and main body portion 116. Alternatively,first and second bifurcated portion 114 and 115 respectively may besingly or jointly formed separately from a main body portion and may bejoined to the main body portion before deployment in the body passagewayor in vivo after such deployment.

First and second bifurcated portions 114 and 115 may be generallycylindrical in shape when deployed, and will generally conform to theshape of a vessel interior within which they are deployed. Their lengthas measured from main body portion 116 may range from about 1 to about10 cm or more. The nominal inflated outside diameter of the distal endsof the first and second bifurcated portions 114 and 115 at cuffs 117 and119 may range from about 2 to about 30 mm, preferably from about 5 toabout 20 mm.

Main body portion 116 comprises a proximal inflatable cuff 111 and anoptional secondary proximal inflatable cuff 112 in fluid communicationwith one or more inflatable longitudinal channels 110. As with otherembodiments, proximal cuff 111 serves primarily to seal graft 100 firmlyagainst a lumen wall. Secondary proximal inflatable cuff 112 has beenfound to confer additional kink resistance on graft 100, particularly inthose clinical applications in which the vessel in which the graft isdeployed is highly angled or tortuous. The nominal inflated outsidediameter of secondary proximal inflatable cuff 112 may range from about10 to about 45 mm, preferably from about 15 to about 30 mm, while thenominal inflated outside diameter of proximal cuff 111 may range fromabout 10 to about 45 mm, preferably from about 16 to about 32 mm. Mainbody portion 116 may range in length from about 2 to about 10 cm;preferably from about 4 to about 8 cm.

Endovascular graft 100 further comprises a proximal connector member118, proximal stent 120, and proximal neck portion 146 all of which maybe similar to those components discussed above in reference to FIGS.2-6. Coupling members (not shown) may join proximal stent 120 andproximal connector member 118 as discussed with respect to theembodiments of FIGS. 1-6. Proximal connector members and proximal stentsas discussed in conjunction with the FIG. 1 embodiment are also possiblefor use in bifurcated graft 100.

In bifurcated embodiments of grafts having features of the inventionwhich also have a biased proximal end that forms an inlet axis angle,the direction of the bias or angulation can be important with regard toachieving a proper fit between the graft and the morphology of thedeployment site. Generally, the angular bias of the proximal end of thegraft, proximal neck portion or proximal anchor can be in any direction.Preferably, the angular bias is in a direction and of a magnitudeconsistent with the mean angulation of the type of lesion (e.g.abdominal aortic aneurysm) intended for treatment with the graft.

As with proximal stent 70 of the embodiments shown in FIGS. 2 and 4-6,proximal stent 120 comprises barbs 121 which are oriented in a distaldirection for reliable anchoring against the direction of pulsatileforces in vivo when the device is implanted in the abdominal aorta, forinstance, to treat an abdominal aortic aneurysm.

One or both bifurcated portions 114 and/or 115 may further comprise adistal connector member 124 and/or 150, a distal stent 128, and a distalneck portion 154. The embodiment of FIG. 7 has distal connector member124 and distal stent 128 disposed at the distal ends of each of firstand second bifurcated portions 114 and 115, respectively. Distalconnector member 124 and distal stent 128 are shown in greater detail inFIGS. 8 and 9.

As discussed with respect to the FIG. 2 embodiment and as shown moreclearly in FIG. 8, distal connector member 124 disposed at or near firstbifurcated portion 114 comprises distal connector member connectorelements 130 and an optional fill-port bridge 132. Fill-port bridge 132serves to prevent interference by distal connector member 124 with themanufacture of graft 100 and with the injection of an inflation medium,while preserving the continuous ring structure of distal connectormember 124.

Inflatable channels 113 (and other inflatable members of the invention)are in communication with a fill port 160 through distal inflatable cuff117. Fill port 160 may be disposed alternatively on second bifurcatedportion 115 or graft main body portion 116, and more than one fill portmay be used. Fill port 160 is configured to accept a pressurized sourceof fluid (gas and/or liquid), particles, gel or combination thereof aspreviously discussed.

As discussed with respect to the FIG. 2 embodiment, FIG. 9 details aflat pattern of distal stent 128, which includes distal stent connectorelements 134. Distal connector member connector elements 130 areconfigured to be coupled with distal stent connector elements 134 viacoupling members (not shown) similar to those discussed with respect tothe FIGS. 1-6 embodiments. Distal stent 128 comprises one or moreoptional distal stent barbs 136, one or more optional distal stent barbtuck pads 138 and one or more optional distal stent barb tuck slots 140,each of which functions in a similar fashion to the correspondingfeatures of embodiments discussed above. Distal stent barbs 136 areoriented proximally, opposite the direction of orientation of barbs 121,to accommodate the environment often found in the iliac arteries thatcan cause the bifurcated portions 114 and 115 to migrate proximally invivo. Note that only two distal stent barbs 136 are shown in FIG. 9 forthe purposes of clarity of illustration despite a larger number beingdepicted in the FIG. 7 embodiment of the present invention. It isunderstood that all embodiments of the present invention includesproximal and distal stents each of which may optionally comprise one,two, or any number of barbs.

The optional distal connector member 150, disposed in the FIG. 7embodiment at or near distal end 152 of second bifurcated portion 115,has a structure similar to that of first bifurcated portion 114, withthe exception of the absence of fill-port bridge 132. Other embodimentsof the invention include bifurcated grafts in which the distal connectormember 150 includes a fill-port bridge.

FIGS. 10-13 illustrate additional features of the present invention thatmay be used in any of the various stents and connector rings of thepresent invention, in any combination.

Turning to FIG. 10, a simplified detail of a proximal apex 93 of thesecond or three-crown region 92 of proximal stent 70 is shown. An outersurface 170 of apex 93 takes on a circular radius of curvature asdefined by circle 172 having a radius r₁. An inner surface 174 of thestent strut apex 93 takes on an elliptical shape as shown by ellipse176. In the configuration of FIG. 10, circle 172 and ellipse 176 offsetas shown by reference numeral 177; however, they may share a commoncenter. Radius r₄ shown at one of the foci of ellipse 176; the foci areshown as separated by a distance 171 in FIG. 10.

We have found that for the NiTi stents used in the present invention,such a configuration provides for a more diffuse strain distribution inthe stent and reduces the peak strains experienced during assembly andin vivo, while also allowing for a smaller delivery profile as comparedto other configurations, particularly in the proximal apex 93 of thesecond or three-crown region 92 of proximal stent 70. However, the stentapex configuration of FIG. 10 may be used in any other stent orconnector member apex described herein, and may be used for componentscomprising material other than NiTi.

In the example of FIG. 10 wherein proximal apex 93 of the second orthree-crown region 92, we have found that for NiTi components radius r₁of between about 0.030 and about 0.070 inch; specifically about 0.050inch is useful, while an offset 171 of between about zero and about0.050 inch; specifically about 0.0025 inch, is effective. A radius r₄ ofbetween about 0.010 and about 0.030 inch; specifically about 0.020 inch,is useful as well.

FIG. 11 details an alternative offset circular apex configuration. Here,a simplified detail of proximal apex 94 in the first or six-crown region90 of proximal stent 70 is shown (without a transition region to thesecond or three-crown stent region as seen in, e.g., FIG. 4 for clarityof illustration). An outer surface 180 of apex 94 takes on a circularradius of curvature as defined by circle 182 having a radius r₂. Aninner surface 184 of apex 94 takes on a circular radius of curvaturedefined by circle 186 having a radius r₃. Radius r₂ may be equal to orgreater than radius r₃ and be within the scope of the present invention.The centers of circles 182 and 186 are offset from each other asindicated by reference numeral 188 in FIG. 11. This offset 188 may beequal to, greater than, or less than the width of the strut 71 in theregion of apex 94.

We have found that when NiTi is used for the stents and connectormembers of the present invention, such a configuration is effective indistributing the peak strains experienced in the stent from the apex 94to stent strut 71 as compared to other configurations, particularly inthe proximal apex 94 of the first or six-crown region 90 of proximalstent 70. However, the offset circular apex configuration of FIG. 11 maybe used in any other stent or connector member apex described herein,and may be used for components comprising material other than NiTi.

When used in the proximal apex 94 of the proximal stent first orsix-crown region 90, we have found offset values ranging from about zeroto about 0.030 inch; particular about 0.020 inch, to be effective inNiTi stents having expanded, or deployed diameters ranging from about 16to about 26 mm. We have also found effective a configuration in whichradius r₂ ranges from about 0.020 to about 0.040 inch; more particularlyabout 0.035 inch, and in which radius r₃ ranges from about 0.005 toabout 0.020 inch; in particular about 0.010 inch.

Optional taper or tapers may be incorporated into the struts 41 and 71of the various stent embodiments of the present invention as well as thevarious proximal and distal connector members. In general, incorporatingone or more tapers into the struts on both proximal and distal stentsprovide greater space in the tapered region to accommodate alternativefeatures such as barbs and tuck pads. It allows for a smaller deploymentprofile when the component is in a radially collapsed deliveryconfiguration. We have found that when configuring the various stentsand connector elements of the present invention into this reduceddiameter delivery profile, the stents experience a large degree ofbending strain that is often poorly or locally distributed. Taperingcertain stent struts in particular locations helps to distribute thisstrain more evenly throughout the stent or connector member and tomanage the peak strains. The examples of FIGS. 12 and 13 are nowintroduced and discussed below.

In FIG. 12, a simplified section of the second or three-crown region 92of proximal stent 70 is depicted in which the stent struts 71 taper froma maximum width 190 (which may or may not equal a width of strut 71 inregion of apex 93) to a minimum width 192. The optional taper, expressedas the ratio of the maximum width 190 to the minimum width 192, may varywidely depending on the particular region of the stent or connectormember, the material used, and other factors. Taper ratios ranging from1 to about 10 or greater are within the scope of the present invention.It is also within the scope of the present invention for the stentstruts 71 to exhibit no taper.

For example, in a proximal stent 70 three-crown region 92 made fromNiTi, we have found effective a maximum strut width 190 ranging fromabout 0.016 to about 0.032 inch; particularly from about 0.022 and about0.028 inch, and a minimum strut width 192 of between about 0.010 andabout 0.026 inch; particularly from about 0.012 and about 0.022 inch.The optional tapered strut feature described herein and shown in FIG. 12may be used in any other stent or connector member described herein, andmay be used for components comprising material other than NiTi.

Turning now to FIG. 13, a simplified section of distal stent 128 isshown as an example of optional tapering that results in asymmetriccrowns. In this example, distal stent 128 comprises a distal apex orcrown 196 exhibiting a width 198 and a proximal apex or crown (withconnector element 134 removed for clarity of illustration) 200exhibiting a smaller width 202. It is within the scope of the presentinvention for width 198 and width 202 to be equal.

We have found that, especially for the distal stents of the presentinvention, an asymmetric crown in which the distal apex 200 has asmaller strut width than that of the proximal apex 196 results in adifference in the expansion force exerted between each of the proximaland distal apices. When deployed in a diseased lumen or vessel, theproximal apices of such a stent having this configuration will tend toexert a smaller expansion force near the graft seal zone, reducing thepotential for such a stent to cause trauma to tissue in the seal zonenear the cuffs (where weaker, more diseased tissue tends to reside).Such a configuration also facilitates a consistent, safe and predictabledeployment when the component moves from a reduced diameter deliveryprofile to an expanded treatment profile. Finally, such a taper reducesthe flare exhibited by the distal apex 200; this in turn provides for asmaller distal stent delivery profile when the distal stent is in areduced-diameter configuration. Taper ratios (defined in the same mannerabove as the ratio between width 198 and width 202) ranging from 1 toabout 10 or higher are within the scope of the present invention.

For distal stent 128 comprising NiTi, we have found that a width 202ranging from about 0.010 to about 0.026 inch; specifically from about0.012 and about 0.024 inch to be useful, and we have found a width 198ranging from about 0.016 to about 0.032 inch; specifically from about0.017 to about 0.028 inch to be useful.

Of course, the various types of offset radii and combinations ofelliptical and circular apex radii may be used to effect these tapersand ratios so to further cause the desired behavior during assembly intoa reduced-diameter delivery configuration, effective delivery andperformance in vivo.

Useful inflation media generally include those formed by the mixing ofmultiple components and that have a cure time ranging from a few minutesto tens of minutes, preferably from about three and about twentyminutes. Such a material should be biocompatible, exhibit long-termstability (preferably on the order of at least ten years in vivo), poseas little an embolic risk as possible, and exhibit adequate mechanicalproperties, both pre- and post-cure, suitable for service in the graftof the present invention in vivo. For instance, such a material shouldhave a relatively low viscosity before solidification or curing tofacilitate the graft cuff and channel fill process. A desirablepost-cure elastic modulus of such an inflation medium is from about 50to about 400 psi—balancing the need for the filled graft to form anadequate seal in vivo while maintaining clinically relevant kinkresistance of the graft. The inflation media ideally should beradiopaque, both acute and chronic, although this is not absolutelynecessary.

Details of compositions suitable for use as an inflation medium in thepresent invention are described in greater detail in U.S. patentapplication Ser. No. 09/496,231 to Hubbell et al., filed Feb. 1, 2000and entitled “Biomaterials Formed by Nucleophilic Addition Reaction toConjugated Unsaturated Groups” and U.S. patent application Ser. No.09/586,937 to Hubbell et al., filed Jun. 2, 2000 and entitled “ConjugateAddition Reactions for the Controlled Delivery of PharmaceuticallyActive Compounds”, now U.S. Pat. No. 6,958,212. The entirety of each ofthese patent applications is hereby incorporated herein by reference.

The 1,4 addition reaction of a nucleophile on a conjugate unsaturatedsystem is referred to as a Michael-type of reaction. Conjugation canrefer to both alternation of carbon-carbon, carbon-heteroatom orheteroatom-heteroatom multiple bonds with single bonds. Usefulconjugated unsaturated groups include acrylate, acrylamide, quinone andvinylpyridinium. Such conjugated unsaturated groups may be present onoligomers and polymers, such as poly(ethylene glycol), poly(ethyleneoxide), poly(vinyl alcohol), poly(ethylene-co-vinyl alcohol),poly(acrylic acid), poly(ethylene-co-acrylic acid),poly(ethyloxazoline), poly(vinyl pyrrolidone), poly(ethylene-co-vinylpyrrolidone), poly(maleic acid), poly(ethylene-co-maleic acid),poly(acrylamide), poly(ethylene oxide)-co-poly(propylene oxide) blockcopolymers, and combinations or copolymers thereof. Useful nucleophilesinclude thiols and amines. Desirably, the conjugated unsaturated systemis polyethylene glycol diacrylate and the nucleophile is a thiol, suchas trimethylolpropane tris(3-mercaptopropionate) or pentaerythritoltetrakis (3-mercaptopropionate).

We have found one particular three-component medium formed by theMichael addition process to be particularly useful in serving as aninflation medium for the present invention. This medium comprises:

-   -   polyethylene glycol diacrylate (PEGDA), present in a proportion        ranging from about 50 to about 55 weight percent; specifically        in a proportion of about 52 weight percent,    -   pentaerthyritol tetra 3(mercaptopropionate) (QT) present in a        proportion ranging from about 22 to about 27 weight percent;        specifically in a proportion of about 24 weight percent, and    -   glycylglycine buffer present in a proportion ranging from about        22 to about 27 weight percent; specifically in a proportion of        about 24 weight percent.

Variations of these components and other formulations as described inU.S. patent application Ser. Nos. 09/496,231 and 09/586,937, now U.S.Pat. No. 6,958,212, both to Hubbell et al., may be used as appropriate.In addition, we have found PEGDA having a molecular weight ranging fromabout 350 to about 850 to be useful; PEGDA having a molecular weightranging from about 440 to about 560 are particularly useful.

Radiopaque materials as previously discussed may be added to this3-component system. We have found that adding radiopacifiers such asbarium sulfate, tantalum powder, and soluble materials such as iodinecompounds to the glycylglycine buffer is useful.

We have found that triethanolamine in phosphate-buffered saline may beused as an alternative to glycylglycine buffer as the third componentdescribed above to form an alternative curable gel suitable for use inembodiments of the present invention.

An alternative to these three-component systems is a gel made viapolymer precipitation from biocompatible solvents. Examples of suchsuitable polymers include ethylene vinyl alcohol and cellulose acetate.Examples of such suitable biocompatible solvents includedimethylsulfoxide (DMSO), n-methyl pyrrolidone (NMP) and others. Suchpolymers and solvents may be used in various combinations asappropriate.

Alternatively, various siloxanes may be used as inflation gels. Examplesinclude hydrophilic siloxanes and polyvinyl siloxanes (such as STAR-VPSfrom Danville Materials of San Ramon, California and various siliconeproducts such as those manufactured by NuSil, Inc. of Santa Barbara,Calif.).

Other gel systems useful as an inflation medium or material for thepresent invention include phase change systems that gel upon heating orcooling from their initial liquid or thixotropic state. For example,materials such as n-isopropyl-polyacrylimide (NIPAM), BASF F-127pluronic polyoxyamer, and polyethylene glycol (PEG) chemistries havingmolecular weights ranging between about 500 and about 1,200 aresuitable.

Effective gels may also comprise thixotropic materials that undergosufficient shear-thinning so that they may be readily injected through aconduit such as a delivery catheter but yet still are able to becomesubstantially gel-like at zero or low shear rates when present in thevarious channels and cuffs of the present invention.

In the case of the three-component PEDGA-QT-glycylglycine formulationdescribed above, a careful preparation and delivery protocol should befollowed to ensure proper mixing, delivery, and ultimately clinicalefficacy. Each of the three components is typically packaged separatelyin sterile containers such as syringes until the appropriate time fordeploying the endovascular graft. The QT and buffer (typicallyglycylglycine) are first continuously and thoroughly mixed, typicallybetween their respective syringes for approximately two minutes. PEGDAis then mixed thoroughly with the resulting two-component mixture forapproximately three minutes. This resulting three-component mixture isthen ready for introduction into the graft body section as it will cureinto a gel having the desired properties within the next severalminutes. Cure times may be tailored by adjusting the formulations,mixing protocol, and other variables according to the requirements ofthe clinical setting. Details of suitable delivery protocols for thesematerials are discussed in U.S. patent application Ser. No. 09/917,371to Chobotov et al., now U.S. Pat. No. 6,761,733.

We have found the post-cure mechanical properties of these gels to behighly tailorable without significant changes to the formulation. Forinstance, these gels may exhibit moduli of elasticity ranging from tensof psi to several hundred psi; the formulation described above exhibitsmoduli ranging from about 175 to about 250 psi with an elongation tofailure ranging from about 30 to about 50 percent.

Notably, we have found it helpful to add an inert biocompatible materialto the inflation material. In particular, we have found that adding afluid such as saline to the PEGDA-QT-glycylglycine formulation(typically after it has been mixed but before significant curing takesplace) lowers the viscosity of the formulation and results in greaterease when injecting the formulation into the graft body section networkof inflatable cuffs and channels without sacrificing the desiredphysical, chemical, and mechanical properties of the formulation or itsclinical efficacy. In the appropriate volume percentages, addingmaterials such as saline may also reduce the potential for the inflationmaterial such as PEGDA-QT-glycylglycine to pose an embolic risk in caseof spillage or leakage. Saline concentrations as a volume percentage ofthe final saline/three-component formulation combination may range fromzero to as high as sixty percent or more; particularly suitable aresaline concentrations ranging from about twenty to about forty percent.We have found a saline volume concentration of about thirty percent tobe most suitable. Alternatives to saline may include biocompatibleliquids, including buffers such as glycylglycine.

In more general terms, it is desirable to use an inflation medium inwhich each of its components is biocompatible and soluble in blood. Abiocompatible inflation medium is desirable so to manage any toxicityrisk in the case the inflation medium were inadvertently released intothe patient's vasculature. A soluble inflation medium is desirable so tomanage any embolism risk if released into the vasculature. Such aninflation medium should not disperse nor gel or solidify if spilled intoflowing blood before curing. In the event of a spill, the normal bloodflow would then rapidly disperse the components and their concentrationwould fall below the level required for crosslinking and formation of asolid. These components would then be eliminated by the body throughstandard pathways without posing an embolic risk to the patient. Amongthe many possibilities of an inflation medium example in which all ofthe components are soluble in blood is the combination polyethyleneglycol diacrylate, a thiolated polyethyleneamine, and a buffer.

As previously discussed, more than one type of inflation medium, or morethan one variant of a single type of inflation medium may be used in asingle graft to optimize the graft properties in the region in which itis disposed.

For example, in the proximal and distal cuffs of the various embodimentsof the present invention, the inflation material serves as a conformablesealing medium to provide a seal against the lumen wall. Desirablemechanical characteristics for the inflation medium in the proximal anddistal cuffs would therefore include a low shear strength so to enablethe cuff to deform around any luminal irregularities (such as calcifiedplaque asperities) and to conform to the luminal profile, as well as ahigh volumetric compressibility to allow the fill material to expand thecuffs as needed to accommodate any late lumen dilatation and maintain aseal.

In the channel or channels, by contrast, the inflation medium servesprimarily to provide structural support to the lumen within which thegraft is placed and kink resistance to the graft. Desirable mechanicalcharacteristics for the inflation medium in the channel or channelstherefore includes a high shear strength, to prevent inelasticdeformation of a channel or channel segment due to external compressionforces from the vessel or lumen (due, for example, to neointimalhyperproliferation) and low volumetric compressibility to provide stablesupport for adjacent channels or channel segments that may be incompressive contact with each other, thereby providing kink resistanceto the graft.

Given these contrasting requirements, it may be useful to have differentinflation materials fill different portions of the graft, such as oneinflation medium for the proximal and distal cuffs and a second in thechannel or channels.

In the various embodiments of the present invention, it is desirablethat the inflation medium be visible through the use of techniques suchas fluoroscopy during the time of deployment in which the graft cuffsand channels are being filled with the inflation medium. Such visibilityallows the clinician to verify that the cuffs and channels are fillingcorrectly and to adjust the filling procedure if they are not. It alsoprovides an opportunity to detect any leakage or otherwise undesirableflow of inflation material out of the graft so that injection may bestopped, thereby minimizing the amount of leaked inflation material.

After the graft has been deployed into a patient, it is desirable thatthe graft be visible through the use of follow-up imaging techniquessuch as computed tomography (CT) and the like. However, the inflationmaterial at this point in time is ideally not so radiopaque that itproduces a dense CT image as such an image could potentially maskclinically significant endoleaks that would be visualized by opacifyingthe blood with a contrast agent.

Balancing these two objectives is difficult, however, since CTtechniques are much more sensitive in detecting small amounts ofradiopaque matter than are fluoroscopy techniques. One solution is touse an inflation medium that becomes less radiopaque over time, such asfor example by using a blend of radiopaque materials in which one ormore will diffuse out of the inflation medium over time, therebyreducing the inflation medium's radiopacity. For instance, a blend of asoluble contrast agent such as an iodinated aqueous solution and aninsoluble contrast agent such as barium sulfate may serve this purpose.The soluble contrast agent will diffuse through the graft body sectionpores some time after the graft has been implanted, resulting in aprogressive decrease in radiopacity of the inflation material over time.A fill material radiopacifier prepared from a combination of about twopercent barium sulfate (by weight) and about 20 percent iodinatedcontrast solution (by weight) is useful in this capacity.

While particular forms of the invention have been illustrated anddescribed, it will be apparent that various modifications can be madewithout departing from the spirit and scope of the invention.

1. An endovascular graft comprising: a graft body section having aninflatable cuff and wherein the inflatable cuff contains athree-component inflation medium, wherein the inflation medium comprisesthe combination of polyethylene glycol diacrylate with pentaerthyritoltetra 3(mercaptopropionate) or a thiolated polyethyleneamine, and abuffer.
 2. The endovascular graft of claim 1 wherein the buffercomprises glycylglycine.
 3. The endovascular graft of claim 1 whereinthe buffer comprises triethanolamine in phosphate-buffered saline. 4.The endovascular graft of claim 1 wherein the polyethylene glycoldiacrylate is present in a proportion ranging from about 50 to about 55weight percent.
 5. The endovascular graft of claim 1 wherein thepolyethylene glycol diacrylate has a molecular weight ranging from about350 to about
 850. 6. The endovascular graft of claim 1 wherein thepentaerthyritol tetra 3(mercaptopropionate) is present in a proportionranging from about 22 to about 27 weight percent.
 7. The endovasculargraft of claim 2 wherein the glycylglycine is present in a proportionranging from about 22 to about 27 weight percent.
 8. The endovasculargraft of claim 1 wherein a post-cure elastic modulus of the inflationmedium is between about 175 and about 250 pounds per square inch.
 9. Theendovascular graft of claim 8 wherein the inflation medium exhibits acure time between about two minutes and about ten minutes.
 10. Theendovascular graft of claim 1 wherein the inflation medium additionallycomprises saline or other inert biocompatible material.
 11. Theendovascular graft of claim 10 wherein the inflation medium comprisesbetween about 20 and about 50 percent by volume saline.
 12. Theendovascular graft of claim 1 wherein the graft body section comprisesan inflatable channel in fluid communication with the inflatable cuff.13. The endovascular graft of claim 12 wherein the inflatable cuff isdisposed at a proximal portion of the graft body section and furthercomprising a second inflatable cuff disposed at a distal portion of thegraft body section and wherein the second inflatable cuff is in fluidcommunication with the inflatable channel and inflatable cuff.
 14. Anendovascular graft comprising: a graft body section having an inflatablecuff and wherein the inflatable cuff contains an inflation medium thatcomprises two components, a buffer, and a radiopaque material comprisingan iodinated aqueous solution.
 15. The endovascular graft of claim 14wherein the buffer comprises a glycylglycine.
 16. The endovascular graftof claim 14 wherein the inflation material becomes less radiopaque overtime.
 17. The endovascular graft of claim 14 further comprising aninsoluble contrast agent.
 18. The endovascular graft of claim 17 whereinthe insoluble contrast agent comprises barium sulfate.
 19. Anendovascular graft comprising: a graft body section having an inflatablecuff and wherein the inflatable cuff contains a three-componentinflation medium that cures via a Michael addition process, wherein theinflation medium comprises a polymer having conjugated unsaturatedgroups, a nucleophile and a buffer.
 20. The graft of claim 19 whereinthe unsaturated groups are selected from the group consisting ofacrylate, acrylamide, quinine, vinylpyridinium and combinations thereof.21. The graft of claim 19 wherein the polymer is selected from the groupconsisting of poly(ethylene glycol), poly(ethylene oxide), poly(vinylalcohol), poly(ethylene-co-vinyl alcohol), poly(acrylic acid),poly(ethylene-co-acrylic acid), poly(ethyloxazoline), poly(vinylpyrrolidone), poly(ethylene-co-vinyl pyrrolidone), poly(maleic acid),poly(ethylene-co-maleic acid), poly(acrylamide), poly(ethyleneoxide)-co-poly(propylene oxide) block copolymers, and combinations orcopolymers thereof.
 22. The graft of claim 19 wherein the nucleophile isselected from the group consisting of thiols, amines and combinationsthereof.
 23. The graft of claim 19 wherein the polymer is a polyethyleneglycol diacrylate and the nucleophile is a thiol.
 24. The graft of claim23 wherein the nucleophile is trimethylolpropanetris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate) or combinations thereof.